1. Field of the Art
The present invention relates to a pump system for supplying an ultraclean liquid to a high-pressure jet washing machine employed in a cleaning process where a high degree of cleanliness is required as in the manufacture of semiconductors, liquid crystals, etc. More particularly, the present invention relates to a plunger pump system with a shuttle valve.
2. Prior Art
The manufacture of semiconductors, liquid crystals, etc. needs a cleaning process that requires a high degree of cleanliness. A jet washing machine used in such a cleaning process is supplied with an ultraclean liquid by a plunger pump system, for example.
FIG. 8 shows the general arrangement of a plunger pump system which has heretofore been commonly employed. As illustrated, the plunger pump system 1 has a plunger pump 2 for supplying a pressurized liquid, and a stop valve 3 for preventing the liquid from flowing out from a nozzle 4 by the supply pressure of the liquid when the plunger pump 2 is standing by. The plunger pump system 1 is adapted to spray a jet of liquid from the nozzle 4 into a jet washing machine 5 only when the stop valve 3 is open.
The plunger pump 2 has a plunger 6 that reciprocates in a cylinder 7 to pressurize the liquid sucked into a pump chamber 9 from a pump liquid supply hole 8 and to discharge the pressurized liquid from a pump liquid discharge hole 10. A check valve 11 is incorporated in the pump liquid supply hole 8 so that the liquid supplied into the pump chamber 9 during the suction stroke will not flow back during the delivery stroke.
The ultraclean liquid that has been pressurized to a high level by the plunger pump 2 is sent to the stop valve 3. The stop valve 3 has a valve unit 12 through which the liquid passes, and a valve driving unit 13 for driving the valve unit 12.
Accordingly, when cleaning is to be carried out, the stop valve 3 is opened to supply the jet washing machine 5 with a high-pressure liquid from the plunger pump 2. On the other hand, when cleaning is not carried out, the plunger pump 2 is suspended in a stand-by state, and the stop valve 3 is closed by the valve driving unit 13 to prevent the liquid in the pump from flowing out to the jet washing machine 5.
In the above-described plunger pump system, however, since the stop valve 3 is provided with a shaft seal mechanism, e.g., a gland packing, a bellows, or a diaphragm, at a sliding portion that connects together the valve unit 12 and the valve driving unit 13, the conventional plunger pump system 1 involves the following problems: generation of dust or powder from the seal mechanism due to friction; leakage of liquid to the outside through the seal mechanism; and failure of the shaft seal mechanism. Also, a special maintenance is required to properly operate the valve driving unit.